Health globes are awesome. The initial design was horrible but the current one is totally ok in my opinion. As a game mechanic, its simply brilliant. Yes, they do look a bit like chinese lanterns but more like... well health globes. Thats what they look like xD
Edit: The picture you show is the old concept of health globes. Im pretty sure of that.
They are blood vessels/orbs... there is some coagulated blood / organ vestige in the extreme parts. In an lore perpective, they are simply something that represents the fact that in sanctuary, killing heals your wounds (at least if you've nephalem powers awekened). Reading the lore background of all 4 health globes related skills gives this sort of insight:
"We are all connected in life and in death. Partake of the spirits of the dead and flourish like the jungle that grows wild after the fire." —Shadewalker Zunimassa
The Witch Doctor's one implies theres some connection between living and dead beigns. Maybe killing someone make it "release" some energy that belongs to living things and you, in your living condition, may absorb it. Taking those spirits also enhance your spiritual/mental condition, in Witch Doctor's case (that why he gets intelect bonus by grabing health globes).
"When the sky bleeds, the crops grow tall. When our enemies bleed, we grow strong." —Chant of the Harvest
The Barbarian one show much less knowlegde about this strange phenomenon, but it cleary says it happens. Killing heals and make you stronger... Chant of Harvest almost sounds like barbarians are harvests lives, not crops.
"If it bleeds you can kill it. Kill this one slowly." —Greyscarr, Veteran Demon Hunter
This Demon Hunter veteran are lecturing sadistic pratices when it's possible. Almost like you will get something back from killing.
"It just doesn't sit right with me. Some of the things these so-called wizards do... They border on necromancy. Or worse! It's just not proper magic." —Venerable Sorcerer Fob Dunar
This cleary shows wizards can DO something that is close to necromancy, at the eyes of this sorcerer. Gathering energy from the dead is what this skill do and what this Fob Dunar seens to be refering as "necromancy".
I think Health Globes 've an background, as showed by those skills. Sanctuary is a entire world made of demon-angel hybrids, each one having hidden godlike powers. Gathering lifeforce from recent killed beigns is not the stragest thing in the context of this game. If you ask me, programming an giant stone to manipulate how the entire world behaves it's far more fantastical and bizarre.
Sanctuary is a world with magic flowing in every corner, Diablo is a very fantastical story. It has some dark tones but still it's an very magical world, as much as Warcraft's Azeroth. Health Globes are certainly within context.